726 



EXPERIMENT STATION RIOCOKD. 



of the method uro as follows: The soil containiiiu- a medium amount of 

 moisture is placed in a thermostat for 48 hours at 'HP C, and nitrogen 

 in the form of annuoiiia and nitric acid is determined. The results 

 thus obtained are assumed to indicate the amount of nitrogen assimilable 

 by oats (the cereal with which the author chiefly experimented). The 

 phosphoric acid is then determined in a solution obtained by digesting 

 the soil for 24 hours with a '2 per cent solution of acetic acid, using the 

 soil and solution in the ratio of 1:4. This gives the available phos- 

 phoric acid. All other assimilable substances are determined bj^ 

 analyzing an aqueous solution obtained ])y shaking for 48 hours 1 part 

 of the soil with 100 parts of water. The results thus obtained serve 

 as a guide in determining the fertilizer needs of a soil. Culture exper- 

 iments made on the basis of such results corroborated the correctness 

 of the judgment based on them. In the present report, which covers 

 the years 1808 and 1899, experiments are described which were insti- 

 tuted to subject the author\s method to further tests. Man}- new soils 

 from various localities in Russia were studied. Not onlv oats, but 

 also barle}", millet, peas, tlax, buckwheat, nuistard, and sugar beets 

 were grown. In all cases the kind of fertilizer required was reliably 

 indicated by the chemical analysis. 



The results of numerous culture experiments to determine the easily 

 assimilable substances in soils of different degrees of fertilit}' carried 

 out during several years are reported. A jneld of oats on 2 kg. of 

 soil of less than 2 gm. of dry grain and 6 to T gm. of dr}^ crop above 

 the ground is considered low; 3 to 4 gm. of dry grain and 6 to 12 gm. 

 of dry crop above ground, medium; over 4 gm. of dry grain and over 

 12 gm. of dr}' crop above the ground, high. The following table gives 

 the mean of the author's figures for easily assimilable fertilizing con- 

 stituents in the soil corresponding to different yields of oats and also 

 Hellriegel's figures for nitrogen: 



Assimilable plant food in the soil corresponding iritli different yields of oats. 



Experiments with barley were more limited than Avith oats. The 

 author concludes, however, that the nitrogen content of the soil cor- 

 responding to a medium yield of barley is 0.0051 to 0.0083 per cent. 

 Hellriegel's figure is 0.0042 to 0.0070 per cent. 



